Thanks for the extra information.
Coughing is a very common complaint that we see in practice regularly. Initially the important issue is to determine where the cough originates….so it can be throat, windpipe, bronchi or lungs. As a general rule (but not absolutely) coughs that are deeper (the lungs in particular) carry greater importance and urgency.
Her breathing pattern is normal and her gums are pink and she is fairly well otherwise so this makes a serious lung problem (like pneumonia) much less likely. Coughed up white foam is generally caused by a mixture of inspired saliva and respiratory tract secretions. We can see this with inflammation/infection in the throat and windpipe primarily but it can originate from the lower bronchi and lungs. Heart disease is common in large dogs and can cause the patient to expectorate a white foamy material. But with heart disease we will usually also see some alteration to the breathing pattern and poor exercise tolerance. She seems ok in that way.
So you can see that there are a few options here and we need to be careful that we don’t presume this to be just a mild upper respiratory allergy or infection. If this persists then she must be assessed by a vet soon.
However her pink gums, good general health and bright disposition suggests we have no imminent serious state so it’s reasonable to treat this conservatively over the next few hours until a vet is available if the problem persists. It may be allergy…perhaps something in the yard (plant species). I don’t see any relevance with the owls and rats though. It may also be a low grade infection as with a pharyngitis or tracheitis. The “dog park cough” you mentioned is usually called Kennel Cough and it is a tracheal cough so it usually manifests as a long series of coughs in a row, but usually without much brought up. I doubt it is that (that was why I asked how long you had the pup and whether she was ok).
If this is an inflammatory cough (allergy or minor infection) we may be able to settle it down in the short term with human medications. The most available for this would be Benadryl Allergy (diphenhydramine). Ensure it is not the combination product (Benadryl Allergy and Sinus). 40 mg would be adequate for her. That would be one and a half of the 25 mg tablets if you have that available. You can repeat the dose every 8 hours if necessary. There are other forms of this medication so please let me know if you’re unsure of the dose.
You could also dose her with a human cough suppressant. Dextromethorphan (Tussinol for dry coughs) is best for this. She could be given a dose of 40-50 mg and it could be repeated every 6-8 hours.
Please note that these medications are for a short term control of the cough and if the cough persists it will need to be investigated by a vet. We still need to consider everything from bronchitis to lung disease, heart disease. Coughing can be an important sign.
Keeping her rested and warm in the meantime is also important. Feed her as normal but avoid milk (it generates respiratory mucus).
I hope I’ve been of help but please contact me back if I can assist further.
Kindest regards, Peter